HDL-associated phosphatidylserine normalizes vessel wall metabolism and architecture in atherosclerosis

Background Atherosclerosis is a lipid-driven, chronic inflammatory disease of the arteries that frequently precedes myocardial infarction and stroke. Aside from lipid accumulation and immune cell infiltration, the arterial wall undergoes further transformations and, recently, smooth muscle (SMC) and endothelial (EC) cells have emerged as key players in this disease. Purpose In this study, we sought to investigate the effect of a high-density lipoprotein (HDL)-like formulation incorporating phosphatidylserine (PS), a negatively charged phospholipid involved in efferocytosis, in the aortic vessel wall in a mouse model of atherosclerosis. Methods We designed a reconstituted HDL formulation enriched in PS (PS@rHDL) and investigated its effects in the aorta at the tissue level in Apoe-/- mice fed a Western diet (WD). Metabolic adaptations after PS@rHDL treatment in the vessel wall were assessed using [18F]-2-deoxy-2-fluoro-D-glucose (18F-FDG), including autoradiography on whole aortas to determine regional tracer uptake. Next, we measured different parameters of arterial wall architecture in the lesion-free descending thoracic aorta by hematoxylin & eosin, Masson’s Trichrome, and Van Gieson staining. Finally, we sought to gain a deeper insight into the effect of incorporating PS into an HDL-like formulation and performed scRNA-seq on atherosclerotic aortic root and arch samples from treated mice. Results Besides a reduction in aortic mass, a lower 18F-FDG uptake was found in aortas from atherosclerotic mice treated with PS@rHDL, with both measures closely approaching values from healthy wild type (WT) mice (Fig. 1). Atherosclerotic mice treated with PS@rHDL showed reduced vessel wall thickness, collagen burden and number of elastin fiber breaks, and this was accompanied by an increase in the density of nuclei in the plaque-free thoracic aorta. The resulting values for all the measured parameters after PS@rHDL treatment were also close to those of healthy WT controls (Fig. 2A-E). Our scRNA-seq functional enrichment analysis revealed an overall downregulation in collagen and extracellular matrix organization genes in the PS@rHDL group. Within SMCs, a relative reduction in the modulated Lgals3-expressing subpopulation was observed in the PS@rHDL group, with a concomitant expansion of the contractile cluster. We also observed a contraction in the WD-associated subpopulation expressing lipid-handling genes, while the canonical EC compartments expanded after PS@rHDL treatment (Fig. 2F-H). Conclusions Collectively, our results demonstrate that phosphatidylserine formulation into an HDL-like composition leads to potent protective/reparative effects on arterial wall integrity in Apoe-/- mice, and could inspire strategies to enhance the atheroprotective properties of HDL-based therapies.Figure 1 Figure 2